Enzymes : Classification Active Sites , Models and Inhibition MCQ

Quick Facts

Enzymes and Their Classification

Enzymes and Their Classification

An enzyme is a protein molecule that acts as a biological catalyst to speed up the metabolic reaction occurring inside the cells.
Enzymes are not consumed during the metabolic reactions.
However, not all enzymes are made up of proteins. Ribozymes are catalytic RNA molecules that have enzymatic action during synthesis of proteins.
Enzymes greatly increase the rate at which reaction takes place.
They help in transforming one energy form into a more usable form.
Many enzymes have been named by adding the suffix "-ase" to the name of their substrate or to a word or phrase describing their activity.
For example, DNA polymerase catalyzes the synthesis of DNA.

Chemical Nature Of Enzymes:
1. Simple Enzymes:

2. Conjugate Enzyme:

It is an enzyme that has two parts- a protein part called apoenzyme (e.g., flavoprotein) and a non protein part named cofactor.
The complete conjugate enzyme, consisting of an apoenzyme and a cofactor, is called holoenzyme.
Active site is formed jointly the apoenzyme and cofactor.

Enzymes are classified according to the reaction they catalyse. There are following types of enzymes:

Oxidoreductases or Dehydrogenases: catalyze the transfer of hydrogen and electrons from one redox system to another.
Transferases: catalyze the transfer of groups from one molecule to another.
Hydrolases: these cause cleavage of bonds using water.
Lyases: also known as synthases; catalyze reactions involving either the cleavage or formation of chemical bonds; cleavage of bond does not require water.
Isomerases: move groups within a molecule, without changing the gross composition of the substrate.
Ligases: these are energy-dependent and are therefore always coupled to the hydrolysis of nucleoside triphosphates